tools: kwboot: Add image type documentation

Add information of all available image types and where they should be
stored. Storage location offsets where documented from the disassembly of
the A385 BootROM image dump.

Signed-off-by: Pali Rohár <pali@kernel.org>

1 files changed, 62 insertions, 0 deletions

diff --git a/tools/kwboot.c b/tools/kwboot.c
index aae7393..7a7dd5b 100644
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -54,6 +54,68 @@
  *   https://github.com/MarvellEmbeddedProcessors/u-boot-marvell/blob/u-boot-2013.01-armada-18.06/tools/marvell/doimage_mv/hdrparser.c
  * - "Marvell doimage Tool", Marvell U-Boot 2013.01, version 18.06. August 30, 2015.
  *   https://github.com/MarvellEmbeddedProcessors/u-boot-marvell/blob/u-boot-2013.01-armada-18.06/tools/marvell/doimage_mv/doimage.c
+ *
+ * Storage location / offset of different image types:
+ * - IBR_HDR_SPI_ID (0x5A):
+ *   SPI image can be stored at any 2 MB aligned offset in the first 16 MB of
+ *   SPI-NOR or parallel-NOR. Despite the type name it really can be stored on
+ *   parallel-NOR and cannot be stored on other SPI devices, like SPI-NAND.
+ *   So it should have been named NOR image, not SPI image. This image type
+ *   supports XIP - Execute In Place directly from NOR memory.
+ *
+ * - IBR_HDR_NAND_ID (0x8B):
+ *   NAND image can be stored either at any 2 MB aligned offset in the first
+ *   16 MB of SPI-NAND or at any blocksize aligned offset in the first 64 MB
+ *   of parallel-NAND.
+ *
+ * - IBR_HDR_PEX_ID (0x9C):
+ *   PEX image is used for booting from PCI Express device. Source address
+ *   stored in image is ignored by BootROM. It is not the BootROM who parses
+ *   or loads data part of the PEX image. BootROM just configures SoC to the
+ *   PCIe endpoint mode and let the PCIe device on the other end of the PCIe
+ *   link (which must be in Root Complex mode) to load kwbimage into SoC's
+ *   memory and tell BootROM physical address.
+ *
+ * - IBR_HDR_UART_ID (0x69):
+ *   UART image can be transfered via xmodem protocol over first UART.
+ *
+ * - IBR_HDR_I2C_ID (0x4D):
+ *   It is unknown for what kind of storage is used this image. It is not
+ *   specified in any document from References section.
+ *
+ * - IBR_HDR_SATA_ID (0x78):
+ *   SATA image can be stored at sector 1 (after the MBR table), sector 34
+ *   (after the GPT table) or at any next sector which is aligned to 2 MB and
+ *   is in the first 16 MB of SATA disk. Note that source address in SATA image
+ *   is stored in sector unit and not in bytes like for any other images.
+ *   Unfortunately sector size is disk specific, in most cases it is 512 bytes
+ *   but there are also Native 4K SATA disks which have 4096 bytes long sectors.
+ *
+ * - IBR_HDR_SDIO_ID (0xAE):
+ *   SDIO image can be stored on different medias:
+ *   - SD(SC) card
+ *   - SDHC/SDXC card
+ *   - eMMC HW boot partition
+ *   - eMMC user data partition / MMC card
+ *   It cannot be stored on SDIO card despite the image name.
+ *
+ *   For SD(SC)/SDHC/SDXC cards, image can be stored at the same locations as
+ *   the SATA image (sector 1, sector 34 or any 2 MB aligned sector) but within
+ *   the first 64 MB. SDHC and SDXC cards have fixed 512 bytes long sector size.
+ *   Old SD(SC) cards unfortunately can have also different sector sizes, mostly
+ *   1024 bytes long sector sizes and also can be changed at runtime.
+ *
+ *   For MMC-compatible devices, image can be stored at offset 0 or at offset
+ *   2 MB. If MMC device supports HW boot partitions then image must be stored
+ *   on the HW partition as is configured in the EXT_CSC register (it can be
+ *   either boot or user data).
+ *
+ *   Note that source address for SDIO image is stored in byte unit, like for
+ *   any other images (except SATA). Marvell Functional Specifications for
+ *   A38x and A39x SoCs say that source address is in sector units, but this
+ *   is purely incorrect information. A385 BootROM really expects source address
+ *   for SDIO images in bytes and also Marvell tools generate SDIO image with
+ *   source address in byte units.
  */
 
 #include "kwbimage.h"